Electric glow-lamp.



No. 685,725. Patented Oct. 29, I91.

w. NERNST;

ELECTRIC GLOW LAMP.

I (Application filed May 259. 1899.) (No Model.) 2 Sheets-Sheet I.

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A TTORNEX No. 685,725. Patented Oct. 29, l90l. w. NERNST.

ELECTRIC GLOW LAMP.

(Application filed May 29. 1899.)

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' Arm/w x UNITED STATES PATENT "()FFICE.

NVA LTI'IER NERNS'I, OF GGTTINGEN, GERMANY, ASSIGNOR TO GEORGE \VESTINGHOUSE, OF PITTSBURG, PENNSYLVANIA.

ELECT RIC G LOW-LAM P.

SPEGLFIGATION formingart of Letters Patent No. 685,725, dated'October 29, 1901.

Original application filed April 28, 1898, Serial No. 679,081. Divided and. this application filed May 29, 1899. Serial No. 718,624. on model.)

To all whom it may concern;

Be it known that I, WALTHER NERNST, a subject of the Emperor of Germany, residing in Gottingen, Germany, have invented certain new and useful Improvements in Electric Glow-Lamps, of which the following is a specification, the same being a division of an application, Serial No. 679,081, filed April 28, 1898.

My invention relates in a general way to the class of devices known as incandescent electric lamps and a method of lighting; but it differs fundamentally from the incandescent lamps and methods heretofore used and involves certain peculiar features and characteristics which justify its classification as a distinct and novel species.

I-Ieretofore all practical incandescent electric lamps have comprised a filament of conducting material, usually, if not always, of carbon, contained within an inclosing chamber from which the air is exhausted. The fact that the filaments heretofore employed will oxidize when heated in the open air has necessitated inclosing them in vacuum-chambers.

. Various refractory materials comprising certain oxids, sulfids, silicates, and other saltlike compositions of metals are specially qualilied to emit light when heated to a high temperature. It has been proposed toutilize the light-emitting qualities of such materials by maintaining them in a state of incandescence by a gas-flame, as illustrated by the wellknown Welsbach burner, for instance.

When the light-emitting qualities of .these refractory materials were to be used in conimpregnate or coat conductors-such, for instance, as platinum, iridium, or carbonwith a refractory materialsuch, for instance, as calcium or Zirconia-and to use the heat dedeveloped in the conducting material for maintaining the refractory material in an incandescent light-emitting condition. Such combinations, however, have been found to be inoperative for any useful purpose. The.

platinum or carbon or other conducting ma-' terial either itself melts or disintegrates or causes the refractory material to crack off or disintegrate.

I have discovered that certain refractory salt-like combinations,particularly oxids usually classed as the rare earths, which are at ordinary temperatures non-conductors of electricity, as that term is usually employed, will when raised to the high temperature of incandescence become sufficiently good conductors to permit the passage of an electric current under moderate differences ofpotential and may be maintained sufficiently heated to retain their thus-acquired conducting qualities by the passage of the electric current thereth rough. These materials when so traversed by electric currents not only emit more light under the influence of a given amount of electrical energy than the ordinary incandescentlamp, but. they also resist decomposition and disintegration even in the open air, and therefore a lamp constructed in accordance with my invention does not require a vacuumchamber, though a vacuum-chamber may be used in certain cases, if desired.

would be not only inappropriate, but to a certhe name glower to the light-giving'por tion and glow-lamp to the lamp itself as being properly applicable.

The materials which I have discovered to possess the qualities above referred to may be classed under the general term of dry The light is emitted,

electrolytes or dry conductors of the second class. By the expression conductors of the second class I refer to those which when in a conducting condition conduct current by electrolytic action.

, Prominent among the materials with which I have obtained excellent results may be mentioned oxid of magnesium or magnesia .and oxid of zirconium or zirconia, also the oxids of yttrium, cerium, thorium, and the like. These materials when in a dry state and at normal temperatures are practically insulators or non-conductors; but when glowers made from them are heated to a state of incandesence they acquire conducting qualities to such an extent that electricity may be caused to pass through them at ordinary low pressures in sufiicient quantities to keep them in the state of incandesence even after the means employed for imparting the original starting heat is withdrawn. Instead of using these materials individually or alone for forming the glower two or more of them may be mixed or combined in varying proportions with advantageous results. Glowers made from a proper mixture of certain of the materials will pass into the conducting state at a lower initial or starting temperature than will a glower made from one of the materials alone and will maintain under the passage of the electric current a luminous condition without deterioration better and for a longer time than will any single one of such materials. It is not, therefore, the mere mixture of such materials that I prescribe, but the utilization of such mixtures on account of their superior properties when brought to and maintained in a luminous condition. These materials even when in their best operating conducting condition have a specific resistance so great with reference to that of carbon that a glower to be used with a given voltage may be much shorterand thicker than the carbon filament of an ordinary incandescent lamp. For instance, a practical glower of, say, onefiftieth of an inch in diameter and one-half an inch in length may be made, which when heated to a low incandesence will become a sufficiently good conductor to be traversed under a one-hundred-volt difference of potential by a sufficient current to bring it to and maintain it at a state of high incandesence. A current of, say, fourtenths of an ampere or thereabout will accomplish this result. As the material has suificient strength to enable it to be used in much longer lengths than that above referred to, it is possible to construct lamps adapted to be operated at very much higher voltages than is practicable with lamps using carbon filaments, a feature which may be utilized to obtain economy of transmission. This feature, in connection with the high efficiency of the lamp, renders it possible to secure either a given illumination with a much higher transmission efficiency than at present obtained or a higher illumination with the present transmission efliciency, or both the illumi nating and transmission efficiencies may be materially increased.

There are numerous different proportions in which the different refractory materials adapted to the purposes of my invention may be used, and there is a very wide range for the selection of the different materials to be mixed together, and therefore I Will attempt only and it will only be necessary to specify one or two examples. Very excellent results have been obtained from a mixture of ap proximately seventy per cent. of'zirconia and thirty per cent. of yttria, (oxid of yttrium.) Another mixture which I have used with good advantage consists of approximately ten per cent. of zirconia, seventy per cent. of thoria, and twenty per cent. of yttria. I have also obtained excellent glowers from a mixture of about seventy per cent. of thoria and thirty per cent. of yttria. Another mixture consists of 0.5 per cent. of ceria and eighty per cent. of thoria, with 19.5 per cent. of yttria. These percentages may be widely varied, and, generally speaking, the oxids of the rare earths are well adapted for mixture in widelyvarying proportions.

The process of preparing the glowers from which I have heretofore obtained the best results when two or more of the oxids are to be used together consists in thoroughly pulver izing and mixing the materials together into very intimate relations, then mixing therewith a binder of clear starch-paste, making a plastic mass which should be thoroughly worked. The water used in making the paste should be clear and preferably distilled to avoid the presence of lime, which is more volatile than the oxids of the rare earths and therefore undesirable. The plastic mass may then be inserted in a press adapted to force the mixture through a small hole of the req uisite diameter, dependent upon the ultimate diameter desired for the glower, and as the material leaves the press it may be hung over a glass rod or laid upon a suitable supporting-surface and allowed to dry. The material acquires sufticient strength when dried to be conveniently handled, and it is then heated to a very high temperature in any suitable manner-for instance,in an oxyhyd rogen flame. It is desirable that as great a specific gravity as possible may be given to the material--that is to say, the smallest diameter for a given mass of a given length. Care should be taken that every part of the glower is brought to a high incandescence. Usually it is advantageous to heat the material gradually, so as to drive off the moisture and the binding material slowly, and thus lessen the liability of the surface becoming cracked. For example, it may be passed through a preliminary heat in a porcelain kiln. The eventual heating, however, should be carried to an extremely high temperature. \Vhen the material has been thus prepared, a proper length, dependent upon the voltage and ourrent with which it is to be used, is mounted between two suitable conducting-wires. The ends may advantageously be fastened mechemically in any suitable wayas, for instance, by inserting them into suitable sockets made by forming into spirals the conducting-wires, which may be of platinum or other good conducting materials which melt only at a very high temperature. The junctions of the glower with the respective wires are then built up by placing thereon in a liquid or paste-like condition small quantities of a cementing material and heating and drying the same in a gas-flame or otherwise. This process is repeated until a firm union is obtained between the respective ends of the glower and the wires. It is advantageous also to make the points of juncture with the wires of larger diameter than the main portion of the glower, for then the points of contact with the wire will not during the operation of the lamp be as hot as the remainder of the glower, and therefore the wires themselves'are less liable to burn off. The paste or cement with which it is desirable to build ,up the ends may be of the same material as Wires and securing electrical connections therewith may be employed.

For the purpose of obtaining the preliminary or starting heating of the glower various different means may be employed. Usually it is desirable that the heat should be applied only during the starting process and then withdrawn, although in some cases it may be desired to continue the extraneous heat while the lamp itself is in operation.

A very convenient starting-heater consists of a coil of platinum wire or other conducting material which may beheated to a high temperature in the open air by the passage of electric currents without being melted. This wire is coiled or otherwise arranged in such proximity to the glower that when heated by the passage of an electric current it will raise the glower to a sufficiently high temperature to cause it to acquire the necessary conducting capacity to permit sufficient current to .flow through it under the influence of the difference of potential of the circuit upon which it is to be used to carry it to a state of high incandescence and maintain it there. When the lamp has once been started, the circuit through the heater may be interrupted manually or automatically, and if it is desired the heater may also be withdrawn from the immediate vicinity of the glower. Instead of imparting the starting heat by the agency of electric currents other extraneous sources of heat may be employed-as, for instance, a

gas-flame or the flame of a lamp, or even a match in some instances.

The temperature to which the glower must be brought in order to have sufficient conductivity to allow enough current to flow through it to maintain itself in that conductive condition varies somewhat with different materials and proportions. Some of the mixtures will produce a glower which when heated to a conductive temperature will fall in resistance so rapidly under the influence of a constant difference of potential as'to permit a current to flow which would be destructive to the glower. With such glowers means should be employed for counteracting this effect and cause the glower to receive and consume only a predetermined amount of current, and therefore remain ata predetermined safe temperature. A convenient means for accomplishing this result with such glowers consists in introducing in series with the glower a correctlyproportioned resistance preferably having a high positive tempera-- ture coefficient and therefore offering an increasing opposition to the flow of the current with increments of current. composed of materials having little or no positive temperature corrections may, however, be used in certain cases. In constantpotential alternating-current circuits reactive coils maybe used in lieu of such resistance, as above referred to. The expenditure of energy in such compensating devices when required may be very low, as their effective resistance may be in some cases as low as two per cent., or even less, of the resistance offered by the glower when in operation if the lamps are used upon circuits having little or no variation in difference of potential--as, for instance, storage-battery circuits. When used upon circuits subject to Wider varia{ tions, it may be desirable that this resistance Resistances should consume as much as five per centior even more. Upon alternating-current'cir v cuits where reactive coils "are used less than this will usually suffice. I p

In the German patent of J ablochkoff, No; 1,630, there is suggested the possibility of heating the edge of a kaolin strip or plate placed betweentwo electrodes separated by an, intervening air-space by means of the electric spark of an induction-coil. method has not been found capable of commercial use and differs from my method and lamp because of the facts, among others, that kaolin is easily melted andthat my illumi- Such a nant is primarily brought to a conducting temperature throughout and not merely along a line or portion thereof, and my'lamp permits the use of currents ofmuch lower pressure. Moreover, heating by means of connection with a glower such as I have described it is possible to give the lamp a simple and effective commercial form and to readily and repeatedly start the lamp.

By the term solid I do not mean that the conductor must necessarily be of solid crosssection, as it might be perforated or hollow; but I mean a conductor which is continuous in distinction from electrodes between which the current is forced to pass through an intervening air-space.

In certain publications relating to the Jablochkoff candleithas also been suggested that the heating of the upper part of a porcelain plate might be brought about by applying thereto a surface coating of gum and carbon or by using some other temporary expedient for leading the spark across the edge of the plate. These suggested constructions are not commercially practical, and they differ essentially from my invention not only in many of the particulars above set forth, but also in lacking any heating-c0nductor which is a permanent part of the structure capable of repeated use. The Jablochkoff devices are not heating devices, but merely devices in the nature of switches for starting the arc. The plate is not rendered conductive by heat developed in the starting device; but if the plate were itself ultimately rendered con ductive it would be because of the heat due to the sparks traversing its surface after the starter has performed its function of starting the are.

In the accompanying drawings, illustrating my invention, Figure l is a view, partly in diagram, of a complete lamp. Fig. 2 is adetail thereof. Figs. 3, 4, and 5 illustrate modifications. Fig. 6 illustrates certain circuit connections which may be employed for operating the lamp. Figs. 7 and 8 illustrate certain other modifications of the organization of apparatus. Fig. 9 is an enlarged View of a glower.

Referring to the figures, C represents a suitable base for supporting the lamp. It is provided with a circuit-closing device D, by means of which the circuit from any suitable source G of electric currents may be completed to the binding-posts c c of the lamp. The light-giving portion or glower A of the lamp is made in accordance with the description hereinbefore given. It is carried by two conductors a a of any suitable character, and these are connected With the terminals 0 c of the lamp. A bridge-piece a may be employed for holding the conductors a a in their proper relative position. A heating or starting conductor B is shown in Fig. 1 as carried upon a glass or other transparent support I), and it incases to a greater or less extent the glower A. The circuit through the heater B is completed from the terminal 0 through the wire 2, circuit-closer or switching device 8, of any suitable character, and conductor 3 to one terminal of the heater, the other terminal being connected by the conductors 4 and 6 to the remaining terminal 0 of the lamp. The terminals 0 c are connected across the circuit L L The glower itself is connected in parallel circuit with the heater by way of conductors 5 and 6 and the supporting-wires a and a WVhen the switches D and s are closed, the current passes through the heater B, raising the glower A to such a temperature as will render it sufficiently conductive to be traversed by a current from the generator. The circuit through the heater may then be interrupted by the switch 8, or in some cases it may remain in circuit while the lamp is in operation; but in such case the watts expended in the heater or.

starting-conductor B should be as few as possible consistent with its function of heating the glower. I usually prefer, however, to so arrange the starting-conductor that its circuit shall be interrupted when it has performed its function of heating the glower to its conducting condition, and in that case the watts consumed in the startiug-conductor during the short time the circuit is closed through it becomes unimportant. The interruption of the starting-circuit may be either manual or automatic, as shown in Figs. 6 and 7, for instance.

The lamp itself may be, if desired, inclosed in a protecting-globe E of any suitable character; but it is not necessary that it should be incased at all, as it will operate in the air. As the light emitted by the glower is very in tense, it may be desirable in some cases to use a so-called opalescent globe or other means to diffuse the light. The globe E may be held in place in any convenient manner, as by clips 6 e, for instance.

In Fig. 3 I have shown the starting-condoctor 13 as carried by a transparent support 11, completely encircling the glower, and I have also shown suitable supporting-clipsf for receiving the ends of the supports a a, so that a glower may be readily replaced. The support H of the starting-conductor is here shown as carried upon a standard 0, extending from the base O. Conductors for establishing a connection with the heater are connected with the binding-posts c and c and the circuit to the glower A is completed through the binding-posts c c and the standards b b In Figs. 4 and 5 a modification of the invention is illustrated, in which a glower is placed at or near the focus of a concave reflector, which at the same time constitutes asupport for the heating-conductor B. This support His here shown as being concave, and it may be of any suitable non-conducting heat-resisting material-such, for instance, as porcelain. The heating conductor may be embedded in the material.

In Fig. 6 I have shown an organization of circuits for automatically interrupting the circuit connections of the starting-conductor B. Thisconsists of a movable core or armature 713 and its solenoid or actuating-coil K. This coil is placed in circuit with the glower A,

and when the current is established through the glower the core is attracted by the solenoid and the switch .9, which is interposed in the solenoid-circuit, is automatically opened and will remain open so long as the lamp is in operation. When the current through the glower is interrupted, the switch will automatically close and be in position for relighting the lamp when desired.

In Fig. 7 I have illustrated a modification in which the support H and the heating-con-- ductor B inclose the glower A when the lamp is not in operation. When, however, a current is sent through the lamp and the heat from the starting-conductor B is no longer required, then the core of the solenoid K will be drawn upward, carrying with it the movable support H,which is thus lifted away from the glower. The circuit of the heating-conductor is closed through an automatic circuitinterrupting device 3 of any suitable character, so long as no current traverses the coil K. When, however, the heater is removed from the glower, the circuit of the heating-conductor is automatically interrupted at the same time. I have shown a spring t suspending the core 7c, so as to render it movable under the influence of a relatively small amount of current.

In Fig. 8 I have illustrated a modification in which the glower itself is moved, while the heating-support H and its conductor 13 remain stationary. In this instance the movement of the core 70 within its solenoid will move the glower out from the inclosing support H. A rod 7', passing through an opening 'r, serves to guide the parts throughout their motion. I have also shown the heater as being supplied from a separate source G of electricity instead of being in a branch circuit from the source G. Such a separate generator may of course be used in other instances. An automatic circuit-interrupting device may be placed in the circuit of the heater in this case as well as in the others, if desired. The interruption of the circuit through the glower automatically restores the parts to the positions shown, and the same is true of Fig. 7.

The initial starting-heat may be given to the glower in other ways than by heat supplied by an electric current. Any source of heat which may be conveniently supplied in sufficient quantities to raise it to its conducting temperature may be used. By these and other similar methods sufficient initial starting-heat may be given to the glower in a few seconds, and the flow of current through the glower itself then generates heat, and thus quickly brings it to a state of high incandescence. The Joule heat thus generated in the glower will serve to maintain this high incandescence and light-emitting condition.

In cases where there is liable to be an undue increase in the amount of current flowing through the glower when placed upon a constant-potential circuit means (such as indicated at may be employed for preventing such an increase. The device R is shown as being placed in series with the lam-p itself and,

as hereinbefore explainethmay consist of a high specific resistancesuch, for instance,

as platinum or iron-and properly proportioned to prevent an increase of current through the lamps except under the influence of an increase of potential. In the case of lamps used on an alternating-current circuit properly-proportioned reactive or impedance coils may be used.

Although I have described the invention more particularly with reference to open-air use, I desire it to be understood that it may also be used in vacuum-chambers, if desired.

This application is a division of application Serial No. 679,081, filed April 28,1898, in which application claims are made upon the, methods of operating electric lights described herein, and in certain other applications, divisions hereofviz., Serial No. 736,122, filed November 7, 1899, and Serial Nos. 55,221 and 55,222, filed April 10, 190lI have claimed certain features of construction described herein;

I claim as my invention- 1. In an electric glow-lamp, a current-carrying glower composed of a mixture of dry electrolytes, conducting-terminals combined therewith, and a heater for imparting thereto a sufficient temperature to render the same a sufficient-ly good conductor to convey such a;

currentas will maintain it in its heated condition.

2. In an electric lamp, a current-carrying glower composed of an intimate mixture of .dry electrolytes which are practicallynonconduct-01's when cold and become fairly good conductors when heated to incandescence,.

conducting-terminals connected therewith, in

combination with a heating device for im-- imparting an initial conductive temperatureto the glower.

4. In an electric glow-lamp, the combination with the current-carrying glower consisting of a material that is'a non-conductor when cold and a conductor when heated to a high temperature, conducting-terminals combined therewith, of an electrical heater therefor consisting of a conductor located in proximity to, but out of contact with, the body of said glower.

5. In an electric lamp, a current-carrying glower which is practically a non-conductor when cold and a conductor when heated, cond uctingterminals combined therewith, in combination with an electric heating device separated from the glower for imparting sufficient heat to the glower to render it conductive, the said heating device consisting of a continuous metallic conductor.

6. In an electric lamp, the combination of a current-carrying glower which is a non-conductor when cold and a cond uctor when heated to incaudesccnce, condnoting-terminals combined therewith, and an electric heater separated from the glower, consisting of a solid continuous conductor for imparting an initial temperature to the glower and thereby rendering it conductive.

7. In an electric lamp, a current-carrying glower which is a poor conductor when cold and a better conductor when heated, in combination with a continuous metallic electric heating device separated from the glower for imparting heat to render it. sufficiently conductive.

S. An electric lamp consisting of a glower composed of an intimate mixture of two or more oxids of the metals of the so-called rare earthssuch as oxids of zirconium, yttrium, thorium, 850., in combination with electric terminals and a holder therefor, and a starting-heater in proximity thereto but not permanently in contact therewith.

9. In electrical incandescentlamps,the combination with an incandescent body that isa non-conductor when cold and a conductor when heated to a high temperature, said body being of sulfieient mass to itself conduct the lighting'current when thus heated, of means out of contact therewith forelectricallyheating said incandescent body, and means for closing an electric circuit through the said body.

10. In electrical incandescent lamps, the combination with an incandescent body that is a non-conductor when cold and a conductor when heated to a high temperature, of a wire resistance combined with a sleeve or mantle of heat-proof non-conductive material, the whole being placed in the vicinity of the said incandescent body, and means for electrically heatingsaid wire resistance.

11. In an electricalincandescent lamp, the combination with an incandescent body that is a non-conductor when cold and becomes a conductor when heated to a high temperature, and a heating-conductor exterior to said body for heating it out of contact therewith, and means for closing an electric circuit through the said body.

12. In an electric lamp, the combination of a rare-earth glower such as described, an elec tric heater separated from the glower consisting of a solid continuous conductor forimparting an initial temperature to the glower and thereby rendering it conductive, and means for automatically interrupting the circuit connections of the electric heater.

13. In an electric lamp, the combination of a light-giving member formed of a material which is a non-conductor at ordinary temperatures and a conductor at high temperatures, an electric heating device adapted to supply heat to said light-giving member to render it conducting, and an electromagnetic device adapted to cause the cessation of said supply when the light-giving member has become conducting.

14. In an electric lamp, an electromagnetic coil, an armature therefor, an electric heater, a circuit-breakercontrolled by said armature, and a glower in circuit with said coil,tl1e aforesaid parts being constructed and arranged so that when a current is established in said glower said coil shall actuate the armature to break circuit through said heater.

15. In an electric lamp, the combination of a light-giving member formed of a material which is a non-conductor at ordinary temperatures and a conductor at high temperatures, a heating resistance receiving energy from the same source as the light-giving member, and an electromagnetic device for automatieally cutting said resistance out of circuit when said light-giving member becomes operative.

16. In an electric lamp, the combination of an incandescent body adapted to form part of an electric circuit and composed of a material which is a non-conductor at ordinary temperatures and becomes a conductor only at high temperatures, heating means therefor, said body and heating means being connected in multiple arc, and means for automatically opening the heating-circuit.

17. An electric glower of the described character connected in circuit with a source of electrical energy, in combination with an electric heating device adapted to heat said glower to the desired current-carrying capacity, together with an electromagnet having its coils located in circuit with the glower and a circuit-interruptcr for the heating-circuit, said circuit-interrupter being operat ively connected with the armature of the electromagnet.

18. The combination of an electric-lamp glower which is a non-conductor of electricity when cold and a conductor when heated to incandescence, a heating-conductor in parallel circuit with the glower, and means for interrupting the circuit connections of the heater when the'current is traversing the glower.

19. In an electric lamp, the combination of a rare-earth glower such as described, an electric heater out of contact therewith for imparting an initial temperature thereto and thereby rendering it conductive, and means for interrupting the circuit connections of the electric heater.

20. The combination with a glower and a heater out of contact therewith, of three conductors leading thereto, one conductor being common to the glower and heater and the other two being connected to the glower and heater respectively, means for controlling the connections of the heating-circuit, and means for opening the connections of the glower.

21. The combination with a glower and a heater therefor, of means for supporting the heater and glower, provided with electromagnetic means for depriving the heater of current, and means for depriving the glower of current to extinguish the light.

22. The combination of three conductingwires, and a glower and heater out of contact with the glower, one conducting-wire being common to the glower and heater and the other two connected to the glower and heater respectively, a switch for controlling the connections to both heater and glower, and a second switch for controlling the connections to the heater.

23. The combination with a pyroelect-rolytic incandescing illuminant, of a conductor of high resistance for heating the illuminant, said conductor having separated convolutions whereby the rays of light are freely emitted from the incandescing illuminant through the heating-conductor.

24. The combination in a lamp, of a glower which is a substantial non-conductor at ordinary temperatures, but becomes a conductor and luminous at high temperatures, an electric heater separated therefrom for raising the glower to a conducting temperature, and a current-restraining device, substantially such as described, formed or adapted to restrict the glower to a predetermined temperature.

25. The combination with a glow-lamp having an originally non conductive glower whose conductivity, when it becomes conductive, increases with increase of temperature, of means for imparting an initial conducting temperature to the glower out of contact therewith, and a conductor in series with the glower composed of a material having a positive temperature coefficient.

26. The combination with a glow-lamp having an originall non-conductive incandescence body or glower composed of a material whose conductivity, after it becomes conductive, increases with increase of current flowing therethrough, of means for imparting an initial conducting'temperature to the incandescence body or glower out of contact therewith, and means for insuring that such increase of current shall be produced only by an increase of applied potential.

27. The combination with a glower which is substantially a non-conductor at ordinary temperatures but becomes a conductor at high temperatures, of a current-restraining device in series therewith, and an electric heater for heating the glower to its conducting tempera- -ture, located in a shunt-circuit around the glower and the restraining device.

28. The-combination with a glower which is substantially a non-conductor at ordinary temperatures but becomes-a conductor at high temperatures, of a current-restraining device in series therewith, an electric heater for heating the glower to its conducting temperature, located in a shunt-circuit around the glower and the restraining device, and means for automatically opening the heater-circuit upon the passage of a predetermined current through the glower-circuit.

29. In an electric lamp, the combination of a glower, a heating-conductor therefor, a solenoid and its core, a circuit-interrupting device for the heater operated by the solenoid and its core, and a steadying resistance for the glower, composed in part of saidsolenoid.

30. In an electriclamp, an electromagnetic 8o coil, an armature therefor, an electric heater supported by said armature, a circuit-breakercontrolled by said armature and a glower in circuit with said coil, the aforesaid parts being constructed and arranged so that when a current is established in said glower said coil shall actuate its armature to move said heater away from said glower and to break circuit through said heater.

' 31. The combinationin an electric lamp, of go a glower,-a support therefor, a movable heater, an electromagnet having an armature actuating said heater, a circuit-breaker controlled by said magnet and circuit connections substantially as described, whereby, when said 5 magnet attracts its armature, said heater shall be moved with respect to said glower, and circuit in said heater interrupted.

32. In an electric lamp, a fixed glower, a-

movable heater, and means actuated by the current traversing said glower for movingsaid heater with respect to said glower. 33. In an electric lamp, and in circuit,

fixed glower, a movable heater, and means ac tuated by the current traversing said glower for breaking circuit through said heater.

34. In an electric lamp and in circuit, a fixed glower, a movable heater, and means actuated by the current traversing said glower for moving said heater with respect to said no glower, and simultaneously breaking circuit in said heater.

35. In an electric lamp, a glower, a heater, and means actnated'by the current established in said glower for altering the proxmovable heater encircling said glower, and

means for moving said heater to and from its encircling position.

37. In an electric lamp, a heater, a glower,

and an electromagnetic device controlling said heater, and constructed to move said r25 heater with respect to said glower.

38. In an electric lamp, an electromagnetic coil, an armature therefor, and an electric heater supported by said armature and a glower in circuit with said coil,- the aforesaid 1 0 parts being constructed and arranged so that when a current is established in said glower, said coil shall actuate its armature to move said heater away from said glower.

39. In an electric glow-lamp, a glower which is a non-conductor .when cold and a conductor when heated to ineandescence, an electric heater therefor consisting of a condoctor and a support therefor in proximity to the glower when thelamp is cold, and means for withdrawing said heater when the glower is operating.

40. In an electric glow-lamp, a glower which is a nonconduetor when cold and a conductor when heated to incandescence, an electric heater therefor consisting of a conductor and a support therefor in proximity to the glower when the lamp is cold, means for separating the heater from the glower when the glower is operating, and a circuit-inten rupter for automatically interrupting the connections of the heater.

41. In an electric lamp, a glower, a heater, means for rigidly holding both glower and heater, and means for varying the distance between said heater and said glower.

42. In an electric lamp, a glower, heater, a rigid arm supporting one of said bodies, means for moving said arm, and means for guiding said arm in a definite path to vary the distance between said heater and said glower.

43. In an electric lamp, a glower, a heater, a rigid arm supporting said heater, means for moving said arm, and means for guiding said arm in a definite path to vary the distance between said heater and said glower.

44-. In an electric lamp, a fixed glower, a heater disposed to one side of said glower, a rigid arm carrying said heater, and a guide receiving said arm and limiting its movement to a direction perpendicular to said glower.

Signed by me at Berlin this 29th day of April, 1899.

WALTI-IER NERNHT.

Witnesses:

WOLDEMAR IIAUPT, HENRY HASPER. 

